Cephalexin Dosing for Skin Infections
For adult skin infections, cephalexin should be dosed at 500 mg orally four times daily (every 6 hours) for 7-10 days, which is the standard regimen recommended by the IDSA guidelines and FDA labeling. 1, 2
Standard Adult Dosing
- The typical dose is 500 mg orally every 6 hours (four times daily) for most skin and soft tissue infections 1, 2
- Treatment duration is typically 7-10 days, adjusted based on clinical response 1
- The maximum daily dose should not exceed 4 grams per day 1, 2
- For mild infections, an alternative regimen of 500 mg every 12 hours may be used specifically for uncomplicated skin and skin structure infections 2
Pediatric Dosing
- The usual pediatric dose is 25-50 mg/kg/day divided into doses given every 6 hours 2
- For streptococcal pharyngitis and skin infections in children over 1 year, the total daily dose may be divided and given every 12 hours 2
- In severe infections, the pediatric dosage may be doubled 2
Clinical Context and Appropriate Use
Cephalexin is appropriate for methicillin-susceptible Staphylococcus aureus (MSSA) and streptococcal skin infections, particularly non-purulent cellulitis without systemic signs of infection. 1
When to Use Cephalexin:
- Non-purulent cellulitis 1
- Impetigo caused by Staphylococcus and Streptococcus species 1
- Penicillin-allergic patients without immediate hypersensitivity reactions 1
- Confirmed MSSA infections 1
When NOT to Use Cephalexin:
Do not use cephalexin for suspected MRSA infections. 1 Instead, empiric MRSA coverage is required for patients with:
- Purulent drainage 1
- Systemic signs of infection 1
- History of MRSA colonization 1
- Injection drug use 1
- Failed initial antibiotic therapy 1
For these high-risk scenarios, use trimethoprim-sulfamethoxazole, doxycycline, or clindamycin instead 1
Practical Advantages
- Cephalexin offers advantages over dicloxacillin due to availability in suspension formulation and less frequent dosing requirements 1
- Research demonstrates that twice-daily dosing (500 mg every 12 hours) can be effective for uncomplicated infections and may enhance compliance 3
- Cephalexin has equivalent efficacy to other first-generation cephalosporins when oral therapy is appropriate 1
Common Pitfalls to Avoid
- Do not assume all skin infections are MSSA-related—assess risk factors for MRSA before selecting cephalexin 1
- Do not continue cephalexin if the patient fails to improve within 48-72 hours; consider MRSA coverage or alternative diagnoses 1
- Do not use cephalexin for necrotizing infections, which require broad-spectrum IV antibiotics and urgent surgical intervention 4